Morbidity and mortality in stranded Cook Inlet beluga whales Delphinapterus leucas

Abstract

The endangered Cook Inlet (Alaska, USA) stock of beluga whales Delphinapterus leucas declined 47% between 1994 and 1998, from an estimated 653 whales to 347 whales, with a continued decline to approximately 312 in 2012. Between 1998 and 2013, 164 known dead strandings were reported by the National Marine Fisheries Service. Only 38 of these animals, or 23% of the known stranded carcasses, were necropsied. Carcasses were found between April and October. The majority of animals necropsied were adults (n = 25), followed by juveniles (n = 6), calves (n = 3), and aborted fetuses (n = 4). Eight of the 11 mature females were pregnant, post-partum, or lactating. Many (82%) of these belugas were in moderate to advanced autolysis, which hampered determination of a cause of death (COD). Each animal had a single primary COD assigned within a broad set of categories. The CODs were unknown (29%), trauma (18%), perinatal mortality (13%), mass stranding (13%), single stranding (11%), malnutrition (8%), or disease (8%). Other disease processes were coded as contributory or incidental to COD. Multiple animals had mild to moderate verminous pneumonia due to Stenurus arctomarinus, renal granulomas due to Crassicauda giliakiana, and ulcerative gastritis due to Anisakis sp. Each stranding affords a unique opportunity to obtain natural history data and evidence of human interactions, and, by long-term monitoring, to characterize pathologies of importance to individual and population health.

Asphyxiation of an Endangered Cook Inlet Beluga Whale, Delphinapterus leucas

“…There was some minor, chronic inflammation in the lungs, and no direct evidence of parasites was observed; however, there were frequent, occasionally mineralized, Splendorehoeppli bodies lining the bronchi and bronchioles. This feature is often associated with lung worms in belugas (Burek-Huntington et al, 2015). A few bronchi in the lungs contained a large amount of debris, including some skeletal muscle (possibly fish), corroborating that some food had been aspirated into the lungs.…”

“That’s how we know they’re healthy”: the inclusion of traditional ecological knowledge in beluga health monitoring in the Inuvialuit Settlement Region

“…The presence of white spots on the liver may indicate a serious illness in affected animals (Vlasman and Campbell 2003). Heart lesions were observed in five Cook Inlet D r a f t beluga, but they were not the cause of death in these stranded animals (Burek-Huntington et al 2015). The liver is currently sampled for biomonitoring, making it a convenient organ to examine regularly, unlike the heart and lungs, which are generally not sampled or examined.…”

Potential natural and anthropogenic impediments to the conservation and recovery of Cook Inlet beluga whales, Delphinapterus leucas

“…Years with mass strandings (total stranded; mortalities associated with that event) include: 1992 (2; 2), 1996 (60; 4 and 20-30; 1), 1999 (58-70; 5), 2003 (46+; 5), 2005 (7; 1), 2008 (28-30; 2), 2014 (UNK; 2) (NMFS 6 : Table 5, p. 62). The event in 2003 occurred on 28 August, during which at least 46 belugas live-stranded in Turnagain Arm for over 10 h; fi ve whales were suspected to have died as a result of this stranding event (Vos and Shelden, 2005), and one was confi rmed by necropsy (Burek-Huntington et al, 2015). In 2014, the NMFS received a report of two stranded beluga whales in Turnagain Arm; however, no live stranding report was received, but necropsy fi ndings suggested they had recently live-stranded which may have contributed to their deaths (Burek- Huntington et al, 2015).…”

“…Four of the adults were single strandings with no signifi cant fi ndings detected. It is hypothesized that large, particularly pregnant, belugas may be more susceptible to mortality following a live stranding event (Burek-Huntington et al, 2015) due to the increased cardiovascular stresses.…”

“…Although only opportunistic data exist on the removal of beluga whales in Cook Inlet due to killer whale predation, a detailed review of stranding and suspected killer whale predation reports from this region mate of approximately one predation event per year, which does not include three CI belugas suspected to have died as a direct result of killer whale predation in which calves accompanied adults that were attacked (Shelden et al, 2003). Injuries on additional belugas were deemed possible killer whale interactions (Burek-Huntington et al, 2015;Hobbs and Shelden 4 ). On 23 Sept. 2000, an NMFS enforcement agent observed 3-5 killer whales chasing beluga whales in Turnagain Arm (Shelden et al, 2003).…”